Glass sealing plug for blasting caps



April 29, 1941. w. w. DURANT GLASS SEALING PLUG FOR BLASTING CAPS Filed Dec. 21, 1958 INVENTOR.

ATTORNEY.

Patented Apr. 29, 1941 GLASS SEALING PLUG FOR BLASTING CAPS Walter W. Durant, Old Greenwich, Conn, assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application December 21, 1938, Serial No. 246,984

1 Claim.

The present invention relates to an electric explosive .initiator of the blasting cap or squib type.

The principal object of the invention is the provision of a sealing plug for the lead wires thereof made of glass or similar material.

Heretofore in initiators of this type, it has been customary to seal the leg or lead wires into a plug of asphaltic or bituminous material with an overlay of sulphur, pitch or the like. Such a combination was particularly objectionable in that there is a tendency for the explosive to ignite fragments thereof and scatter such glowing or blazing particles throughout the explosion area with consequent ignition of carbon monoxide, coal dust or other explosive matter present in the blast area.

It is an important object of the invention, therefore, to provide an electric initiator of the type described in which the head or plug is not only of a non-combustible material but one which will at the same time be inexpensive, simple to manufacture and assemble and which may be made to constitute a waterproof seal for the explosive material within the initiator.

To this end, the invention contemplates in its broadest aspect a plug of glass or the like within which the lead wires are sealed, all within an electric explosive initiator assembly. The invention is also specifically concerned with the combination of such a plug enclosed in a sleeve, said sleeve bearing a specific relationship to the shell within which the plug and charge is contained.

The invention further consists in the novel arrangement, combination and construction of parts more fully described later and shown in the accompanying drawing.

In the drawing- Fig. 1 is a sectional elevation of a typical electric explosive initiator showing one method of applying the glass seal thereto; ti Fig. 2 is a similar view of a modified construc- Referring now with particularity to Fig. '1, an ordinary cylindrical shell is shown at I of thin gilding metal, copper, aluminum or the like and is adapted to contain a secondary or main charge 2 and a primary or initiating charge 3. The

specific nature of these charges plays no partin the present invention and, consequently, may be of any desired chemical composition or mixtures of compositions.

A short open-ended sleeve 4 of metal or other material having substantially the same coefflcient of expansion as glass carries within it a glass plug 5 having embedded therein lead wires 6. It is preferable, of course, that the glass in a plastic or molten condition be poured into the sleeve 4 and around the lead wires so as to form a watertight bond therebetween.

As shown, the ends of the lead wires 6 project below the plug 5 and are provided with a resistance bridge I as is usual in these cases.

The shell I having been filled with the charge of any desired type, the lower rim of the sleeve 4 is placed upon the upper rim of the shell I and the two parts soldered or otherwise secured together as at 8.

While in Fig. l the ignition head including the glass plug is of the open bridge type, yet obviously the same construction may be used in those of the pasted and match head type.

Where desired, a final fill 9 of waterproof thermoplastic material may be added although this is not necessary. It is preferable, of course, that if such a fill or seal is used, it should also be of a non-combustible, non-inflammable substance of which chlorinated diphenyl is typical.

A modification of the invention is shown in Fig. 2 wherein the sleevel carrying the glass plug 5 is of smaller diameter than that of the shell. In such case, and as shown, the sleeve and its assembly of plug and lead wires is inserted within the upper portion of the shell and pushed down far enough for the bridge I to be in proper proximity to the initiator charge 3. In this case, the sleeve is so proportioned that when this relationship exists, the upper edge thereof and the upper edge of the shell are substantially fiush. The two rims may then be joined as by solder 8. As in the case of Fig. l, a waterproof fill may be provided, although this is not an essential.

From the above, it will be readily appreciated that a plug and ignition head has been provided which does not contain a combustible or inflammable substance and which may be used to make a-water-tight seal between the sleeve containing it and the lead wires passing therethrough.

Such glass plugs are cheap, may be readily cast in placeand the entire combination assembled with rapidity to produce an eflicient electric explosive initiator.

While the invention has been shown and described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted only by the scope of the claim.

I claim:

An electric explosive initiator including a shell having an explosive charge therein, a plug head including electric lead wires and ignition means, said plug headincluding a sleeve, a mass of glass within the sleeve and bonded directly to the inside of the sleeve and the outside of the lead wires in a water tight manner, the sleeve being secured to the shell.

WALTER W. DURANT. 

